Physical Therapists Using Clinical Analysis To Discuss The Art And Science Behind Running and The Stuff We Put On Our Feet

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Mizuno Wave Sky Waveknit 4 Multiple Tester Review

The Wave Sky underwent a huge overhaul when it reached its third iteration last year with the loss of the infamous wave plate and introduction of XPOP foam. The Wave Sky 4 is another step forward, but carries much of what people grew to love in the Wave Sky 3. This shoe incorporates 3 midsole foams that work in concert with one another, including the first full length Mizuno ENERZY midsole. This shoe emphasizes comfort, cushion, and durability for lots of miles.

Specifications (per Mizuno Tech Sheet)
Weight: 11.2oz (men's size 9), 9.4oz (women's size 7)
Stack Height: not listed
Drop: 10mm
Classification: premium daily trainer


Nathan: The Mizuno Wave Sky 4 is a great example of an update that improves the previous model by one click forward. The upper is slightly thinned out and more secure, the ride is more stable, and the ENERZY foam adds some propulsive feeling to the ride. This shoe is highly cushioned, soft, yet still has a little bounce as well. This shoe is built to last, and could be considered a comfortable tank.

David: A comfort daily trainer that still has some pop! The Mizuno Wave Sky Waveknit 4 improves on the previous model with 2 major updates. 1 being the introduction of full length Mizuno Enerzy foam complimented with a U4ic topsole. The other is an updated lacing system to help with lockdown. A little heavy, but the bells and whistles make it a nice shoe.

Matt: A solid daily trainer for high mileage running, the Mizuno Wave Sky Waveknit 4 feesl like a lightweight tank. A solid sole that has a surprising amount of bounce to it with a very comfortable and thick waveknit upper. There is a ton going on with this shoe but each piece has an important purpose!


The Wave Sky 4 certainly fits true to size. That said, it does fit slightly on the shorter side, and I noticed a little rubbing at the lateral toe box at the tip of my 5th digit (pinky toe) on the first run. However, this did improve and never caused any friction or blisters. The toe box is also on the wider side with ample room and nice stretch from the Waveknit upper.  The refining of the Waveknit upper in this version (which seems the same as the Wave Rider 24 upper) includes synching up the midfoot lockdown and thinning out the tongue and heel cushioning. This led to a much more secure fit on such a soft footbed. Overall the upper has been thinned out and is breathable, but on the hottest of days the Waveknit does retain a bit of heat.

David: The Wave Sky 4 fits true to size. I agree with Nathan in that it is a little shorter in length, though I did not have any rubbing on my end. The upper has thicker and thinner sections throughout the knit designed to be either non-stretch or stretch depending on the flex points. The tongue holds down the foot well on the dorsum. The heel is padded well, but I had small translation with turning situations, this was fixed with a heel lock. It is on the thicker end and can retain some heat, but breaths decent enough in most situations.

Matt: The Wave Sky Waveknit 4 fits me true to size in my normal size 10. Initially the waveknit felt like it was a tad short on 1st toe, but that broke in within a few minutes. The fit is above average in the toe box, with decent room in the midfoot and an average fit in the heel. The waveknit upper stretches very well in the forefoot and there is plenty of room. The heel collar has a ton of cushioning and the redone midfoot lacing meant I did not have to lace lock the Wave Sky Waveknit 4. The upper is still quite thick, but the tongue has been thinned out and sits very well against the foot. This thickness does predispose this shoe to running warm.  Overall this is a plush upper that does run a little warm, but is very comfortable.


The midsole is made up of three compounds: Mizuno ENERZY (lower full length sole), U4IC (topsole), and XPOP (sandwiched in between). For those who enjoyed the ride of the Wave Sky 3 will find the same cushioned and soft ride without it feeling mushy. The XPOP carries the same bounce as it did in the previous version, but the shoe gets a bit more of a responsive feel from the full length ENERZY midsole. Heel strike is nicely cushioned, and the transition is smooth. The forefoot also feels very soft in the forefoot, particularly later in runs. From my experience in my 15 miler in these, the shoes feel softer as the miles progress. Overall, this shoe feels very protective.

David: This is a multi-foam ride that comes with the Wave Sky 4. The 3 foams are all full length and feature Mizuno Enerzy, U4ic, and XPOP. Enerzy softens the ride a little and helps with a faster transition throughout the shoe, U4ic acts as a topsole to stabilize the softer foam. XPOP gives the bouncing sensation that one experience with the shoe. With all of the foams the shoe comes off as plush with some decent firmness still present with a very protective feel. Thanks to the better midfoot lockdown from prior models the midfoot feels much closer to the platform of the shoe and transitions smoother without translation. I also think the balance of the foams also makes the shoe much less clunky from prior models. Overall it is a smooth ride for those who long a softer protective feel with smooth but not necessarily fast or springy toe off. The drop is at 10mm but feels a little lower and more fluid with the reaction of all of the foams. This is more of a leisure daily mileage shoe.

Matt: The ride of the Wave Sky 4 has a variety of flavors depending on the use. My initial runs in this shoe felt fairly firm and stable. There is plenty of shoe between your foot and the ground, yet the firmer feel to me still gave good ground. This is a protective ride for sure. The heel was a little stiff at first, but broken in with a smooth transition after 10-15 miles. The forefoot has good flexibility thanks to the deep flex grooves, so the toe off is quite smooth. As the miles progressed, the sole begins to soften. After 10-15 miles, the XPOP feels a little more apparent with the softer ride, but the Enerzy sole still has plenty of protection and turnover for a shoe of this weight. The ride feels like a lighter shoe, but as mentioned there is still tons of protection.  Just know the ride is firm at first and takes a few miles to break in.


This is the most improved area of the shoe compared to the Wave Sky 3. The full contact outsole and wider platform does offer some of the stability. However, most of the stability improvement comes from the more secure midfoot lockdown of the upper. The soft nature of this shoe leads to increased demand of intrinsic foot stability and dynamic ankle stability, so for those who need a higher amount of stability but like the high cushion may want to check out the Horizon line.

David: The Wave Sky 4 is on a comeback tour with stability. I had some problems with stability in the prior model but this one is improved. Before I had problems in the midfoot that was improved drastically with the lacing update. The heel isn't horrible with stability but does feel a little better with lace lock. The full contact outsole helps with stability especially with the 3 softer foams. For a softer leisure day shoe the stability isn't too bad! I'm definitely going to keep more road or packed dirt though since you start to notice some instability with grass or choppy conditions. So in summary, not amazing, but not horrible either. On the higher end of stability for a shoe that should run more unstable just by design.

Matt: The Mizuno Wave Sky Waveknit 4 is a neutral shoe. There are no traditional methods of stability present. That being said, the stability is a HUGE step up from the last version. I had a hard time logging longer miles in version 3 and all of that has been addressed in version 4. The Enerzy sole is bouncy but firmer, providing a stable feel from heel to toe. The XPOP is contained nicely, so the softness that comes with time is still controlled. The improved midfoot lock down holds the foot really well. Those who need more stability will need something like the Horizon (REVIEW). For a neutral shoe however, the Wave Sky 4 Waveknit provides enough for those with mild stability needs.


This shoe is most successful for recovery runs, long runs, and aerobic runs. It may be 11.2 oz, but the geometry of the shoe and responsive ENERZY and bouncy XPOP allow this shoe to be fine for daily miles for many. Clearly this shoe is not a performance trainer, and that isn't its design. However, for those looking to complete a marathon, possibly their first, this could be a great option for traveling the distance with a lot of protection underfoot.

David: Definitely best for leisure days and easier runs. The shoe is on the heavy side being at 11.2 ounces. Despite this, if you really ask the shoe to move it will respond pretty well. The XPOP and Enerzy respond to the higher force load and give some pop to the shoe when the pace picks up. This is noticed most ironically after taking a break. You feel the pop again once you start moving again!

Matt: This shoe is meant for easy runs, recovery runs, long runs and mileage. At 11.2 oz for a men's size 9 (almost 12 oz in my size 10), this is a heavy shoe. The Enerzy and XPOP do make this shoe feel lighter and I have been able to do some strides and light fartleks in them, but this is not a performance shoe. If you push hard into the shoe, it will respond thanks to the foam compounds, but you are going to have to push hard.


This thing is a tank. The outsole is showing no wear, which is consistent with previous models and basically all of Mizuno. Additionally, the Waveknit upper is robust and has not lost its security. Finally, the midsole compounds are only feeling better after the testing miles and I expect the trifecta of foams to last at or beyond factory standards.

David: I am not sure I will ever see the day Mizuno durability falls. Yeah... its a comfy tank. Even the waveknit upper is secure and has a strategic build with rigidity in some regions and flexibility in others. The outsole will last for a very long time. The 3 foams should last long even with only road use. No durability concerns here.

Matt: To echo the Nathan and David, this shoe gets Tank status. I have 40 miles on my pair and can't even make a dent in the outsole. The sole has slightly softened, but in a positive way. The upper remains quite durable and actually fits even better now to my feet then when I started. So huge points on durability. I expect far more than 500 miles out of these.


The Wave Sky is the high cushioned, neutral trainer from Mizuno. The Wave Sky 3 was rather unstable for all of our testers, and this version was a big step forward in terms of stability. The two major changes to the shoe are the addition of Mizuno ENERZY and the refinement of the upper. I wouldn't expect the ENERZY foam to be what contributed to the increased stability in the shoe, particularly given that the shoe has increased cushion compared to U4IC based on Mizuno's testing of the material. Imagine standing on a single leg on firm ground versus a pillow. The softer things are, the less stable. Therefore I do not see the ENERZY foam being what improved the stability. Instead I think the improvement comes from the refined upper. This upper locked down the foot much better on the platform. With security from above, the lateral ankle stabilizers and intrinsic foot muscles don't need to do the work of keeping the foot on the platform. This allows them to simply assist in typical progression through the running gait cycle without having to pick up extra stability work. Long story short, upper security is important and can really improve the stability of a shoe. Given that the Waveknit is designed much more securely in the midfoot and does not stretch overtime, this shoe is much more stable.


Mizuno continued to take steps forward with this model. One area that could see some progress is continuing to thin the upper, or possibly offer a mesh version of this shoe for those who like something a bit thinner and lighter.

David: I like the recommendation that Nathan has with a mesh version for those who like that option. I consistently always seem to favor the Waveknit version of models but there is a loyal mesh following within the Mizuno fanbase. I would also like to see the lockdown in the heel region improved a little more but overall I am happy with shoe.

Matt: The upper and sole changes are great compared to version 3. My only suggestion is to consider lightening up this shoe. I know it is a premium cushioned trainer, but a little lighter would not hurt. For every 100g increase in weight, there is a 1% decrease in efficiency. So every bit counts!


For people looking for a very protective shoe that is highly cushioned, soft, yet has some bounce, the Wave Sky 4 could be a great option. This is a durable and comfortable tank for those who want to load on the miles for any distance.

David: Leisure, care free, and easy days. This is a shoe that loves daily mileage. Even for the weight the shoe does have enough pop to tackle some long runs as well, but this is more of your daily workhorse trainer. For those who like to log high mileage in roads and likes protection with a slightly softer landing compared to most daily trainers this could be an option worth looking at.

Matt: For those looking for a toe, protective shoe with an evolving personality, the Wave Sky 4 is a great option. The fit is improved and makes for a comfortable fit with some break in, although may be a little better during the winter. The ride has a smooth toe off and a ton of protection to help you handle long miles and recovery runs without being unstable. Definitely a long distance shoe for getting miles in.


Fit                     8.5/10 (slightly short and just a bit thick on the hottest days)
Ride                  9/10 (very smooth, just a bit heavy)
Stability            8.5/10 (much improved lock down which improved stability on the platform, soft nature does require intrinsic stability from the runner)
Speed                8/10 (performs well at speeds that it is designed for, not for speed)
Durability         10/10 (another tank from Mizuno)

Fit                     9/10 (some heel translation, thicker upper retains some heat)
Ride                  9.25/10 (A bit heavy but smooth, toe off not very quick, poppy for weight)
Stability            8.5/10 (Overall average stability, softness decreases, but lockdown increases)
Speed                8/10 (Great for leisure day. Still has a little bit of pop for weight)
Durability         10/10 (I'm tired of saying tank. Humvee)

Fit                     9/10 (fits a little short at first and thick upper, but conforms really well to feet)
Ride                  8.5/10 (A bit heavy, but smooth toe off. Clunky at first)
Stability            9/10 (Good stability for a neutral shoe)
Speed                6.5/10 (Definitely a protective trainer, )
Durability         10/10 (Not even I can make a dent in these)
Total Score: 87.8% (M: 8.6/10  D: 8.95/10 N: 8.8/10 )

Thanks for reading!

Dr. Matthew Klein is a 140 lb male with notable PRs of 14:45 for 5k and 2:32:44 for the full marathon.  He typically runs 70-100 miles per week and trains at a variety of paces from 8min per mile recovery runs to 4:40 per mile 1k repeats.  He prefers firmer and responsive shoes with snug heels and medium to wide toe boxes.  He is particular to less cushioned shoes and close to the ground shoes, but can handle a little cushion when he gets beat up.

Dr. David Salas is a 135 lb male with notable PRs of 3:54 1500m, 14:56 5k, 31:06 10k, 1:08 for half marathon. He typically runs 40 to 50 miles per week and trains from about 7:30 recovery runs to fast shorter efforts at 4:30 pace. He normally prefers neutral shoes with a firmer ride, but is completely open to other types of shoes.  He is a footwear enthusiast at heart and will always appreciate a high quality shoe when it comes around. For updates on training or testing, IG handle: @docsofrundavid

Dr. Brown is a 155 lb male with notable PRs of 18:18 5K, 39:25 10K, 1:29:01 half marathon, and 3:54 marathon. He typically runs between 20-40 miles per week at a variety of paces from 7:30-8:30 min/mile for recovery runs to 6-6:45 min/mile for tempo runs. He typically prefers shoes that provide some cushioning underfoot but still maintain a more firm and responsive feel. Current goals for 2020 are to break the 1.5 hour half marathon and 3:30 marathon. IG handle: @nate.docsofrunning

Editor's Note: As always, the views presented on this website belong to myself or the selected few who contribute to these posts. This website should not and does not serve as a replacement for seeking medical care. If you are currently injured or concerned about an injury, please see your local running physical therapist. If you are in the Los Angeles area, I am currently taking clients for running evaluations.

Doctor of Physical Therapy
Board Certified Orthopedic Clinical Specialist
Fellow of the American Academy of Orthopedic Manual Physical Therapists

Nathan Brown PT DPT MS
Doctor of Physical Therapy 
Masters in Anatomy and Clinical Health Science
Movement Performance Institute Certified in Advanced Functional Biomechanics 

David Salas PT DPT CSCS
Doctor of Physical Therapy
Certified Strength and Conditioning Specialist

***Disclaimer: These shoes were provided free of charge in exchange for a review.  We thank the  people at Mizuno Running North America for sending us a pair.  This in no way affected the honesty of this review. We put at least 35-50 miles on trainers and 10-25 miles on racing flats prior to reviewing them. Currently we have 40 miles (Matt), 38 miles (Nathan) and 36 miles (David) on our pairs. Our views are based on my extensive history in the footwear industry and years testing and developing footwear. If you are a footwear rep looking for footwear reviews or consultations on development, we are currently looking to partner with companies to assist, discuss and promote footwear models. Partnership will not affect the honesty of our reviews.

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